The stomach of the ruminant is made up four compartments.
Fore stomach (the rumen, reticulum and omasum)
Abomasum (the true stomach)
The rumen is the largest stomach compartment and consist of several muscular sacs, the cranial sac, ventral sac, ventral blindsac, and reticulum. The lining of the rumen wall is covered in small fingerlike projections called papillae, which are flattened, approximately 5mm in length and 3mm wide in cattle sacs. It can hold 25 gallons or more of material depending on the size of the cow. Because of its size, the rumen acts as a storage for feed. A side from storage, the rumen is also a fermentation vat. The rumen’s environment favors the growth of microbes. These microbes digest or ferment feed within the rumen and make volatile fatty acids (VFAs). VFAs are the main energy source of the animal. The rumen absorbs most of the VFAs from fermentation.
The reticulum is a pouch-like structure in the forward area of the body, close to the heart. The tissues in the reticulum form a network similar to honeycomb. A small tissue fold lies between the reticulum and rumen, but the two aren’t separate compartments. Together they’re called the rumino-reticulum. The main function of the reticulum is to collect smaller digesta particles and move them into the omasum while the larger particles remain in the rumen for further digestion. The reticulum also traps and collects heavy/dense objects consumed by the animal. The digestion of fibrous feeds begins is the rumino-reticulum through the mediation of microbes (bacteria, protozoa and fungi), which are normal inhabitants of the three fore stomachs. Microbial digestion commences in the rumen and continues in the reticulum and the omasum, finally ending in the abomasum and intestine.
The omasum is a globe-shaped structure containing leaves of tissue (like pages in a book). It absorbs water and other substances from digestive contents. Feed material (ingesta) between the leaves will be drier than ingesta found in the other compartments.
The abomasum is the only compartment lined with glands. These glands release hydrochloric acid and digestive enzymes, needed to breakdown feeds. The abomasum is similar to a non-ruminant stomach.
Basic principles of ruminant nutrition
The digestion of fibrous feed is carried out by microbes that normally inhabit the rumen. The microbial population is made up of several types of organisms. The efficiency of digestion in the rumen depends on the level of activity of these microbes, which in turn depends on the rate of microbial growth, the density and the composition of the microbial population.
The feed consumed therefore has to provide the nutrient requirements of the microbes in terms of volatile fatty acids, ammonia, minerals and other co-factors. Since growth and activity of rumen microbes depend on the availability of nutrients required by these microbes, the diet should provide a balanced nutrient environment in the rumen, which will cater both to the needs of the microbes and the animal. Such an environment will greatly enhance the breakdown of fibrous feeds.
The digestion of fibrous feeds begins is the rumino-reticulum through the mediation of microbes (bacteria ,protozoa and fungi), which are normal inhabitants of the three fore stomachs. Microbial digestion commences in the rumen and continues in the reticulum and the omasum, finally ending in the abomasum and intestine. The difference in the process of digestion in the fore stomachs, is that the digestion occurs by the action of microbial enzymes, while in the abomasum and intestines this occurs by the action of digestive enzymes. Microbial enzymes also have the ability to utilize non protein nitrogen, like urea to synthesize bacterial protein.
Utilization of rumen breakdown products in bacterial protein synthesis
The volatile fatty acids, ammonia and minerals are utilized by microbes to produce microbial protein, for growth and multiplication. When these microbes eventually pass down into the intestine, they are themselves digested by enzymes into amino acids, soluble carbohydrates, minerals and vitamins.
When these microbes eventually pass down into the intestine, they are themselves digested by enzymes into amino acids, soluble carbohydrates, minerals and vitamins.
The rumen non-degradable protein that flow into the small intestine is digested along with the microbial proteins.
Animal receives protein from two sources
1. Rumen non-degradable or by-pass protein
2. Microbial proteins, it is the major source
The absorption of end products of digestion takes place through the rumen wall as well as through the intestinal wall.
For optimum digestion, the microbes require:
1. A rumen environment with a balanced supply of nutrients
Ammonia
VFA
Soluble sugars
Minerals
2. An optimum pH ( 6 . 9 )
The rumen ammonia concentration plays a critical role. The effect of rumen ammonia concentration on intake and the digestibility of fibrous feed is depicted in below Fig.
The effect of ammonia concentration in rumen liquor on the intake and digestibility of fibrous feed
As shown in the figure, the optimum concentration of rumen ammonia nitrogen is in the range of 180- 200 mg/litre of rumen fluid.
If the rumen ammonia nitrogen concentration is lower than the optimum
The population of microbes will decline
The rate of digestion will slow down
Resulting slower rate of passage of ingested material from the rumen
A lower concentration of rumen ammonia concentration usually occurs due to ingestion of poor quality fibrous feed, which is low in digestible proteins.
In contrast, providing of low quality fibrous feed with feeds that are rich in protein, such as concentrates or feed supplements, soluble sugars and minerals, will help to maintain the rumen ammonia nitrogen concentration at the optimum level.
Thereby increasing bacterial multiplication and digestion of fibrous feed
When the microbial growth and population are high,
The rate of fermentation is high
The feed consumed disappears faster from the rumen, creating more room
Allowing the animal to eat more feed
The animal thus benefits in two ways
It obtains more nutrients, through more efficient fermentation of the feed.
Increasing the amount of feed consumed.
Characteristics of fibrous feed material
1. Fibrous feed material are those that are not digested in the monogastric animal.
2. They contain high fibre due to the presence of ligno-cellulose material in cell walls
3. Low quality grasses and crop residues contain low (2-10%) crude protein and high (65 - 75 % ) cell wall fibre
Main categories of fibrous feed in tropical countries
1. Natural pasture and fodder - which provides the bulk of the feed
2. Fibrous residues from crops grown for human food - like straw and stover from cereal crops such as rice, sorghum, millet and maize.
3. New feed resources from crops - like sugar cane (molasses and sugar cane tops) and multipurpose trees.
4. Other industrial by-products and residues - like canary wastes, brewery wastes and spent tea leaves.
Fibrous crop residues constitute a large potential resource, which has not been extensively used by farmers as feed, because they are not palatable and not readily accepted by ruminants. They contain high levels of coarse fiber that is not easily digested by animals, maintained under traditional feeding systems.
However, scientists have recently shown that these materials have a high potential value as feed, when given with supplementary feeds that are able to balance the nutrients deficient in fibrous feeds.
If the ruminant, given the optimum rumen environmental conditions are able to digest fibrous feeds and release large quantities of nutrients which the animal can use.
Problems associated with the use of fibrous feeds
The nutritive value of fibrous feeds and limitations of use as feed for ruminants.
In general, famers do not consider fibrous materials as suitable for use as feed, because they are not eaten readily by animals. This is due to low palatability and low digestibility.
The low digestibility is due to the high fiber content (more than 18%), low essential nutrients such as soluble sugars and proteins, minerals and vitamins and in some instances due to the presence of "anti-nutritive" factors
Non conventional fibrous feeds and other feed resources
Generally, there is a plentiful supply of non-conventional fibrous material available around farmers' homesteads[garden] that could be easily used as feed for cattle and buffaloes.
These materials can be classified as
1. Agricultural crop residues
2. Agro-industrial by-products.
1. Crops residues
There are at times plentiful supplies of crop residues available in and around the rural households.
Almost all of these materials are at present unutilized
Examples of commonly available crop residues are:
1. Cereal straw from rice, millet and kurakkan
2. Stover from maize and sorghum
3. Plant residues like green gram, cowpea, ground
nut and soya bean
4. Other crop residues like sugarcane tops, sweet potato vines and manioc leaves
2. Agro industrial by products
Most of the agro-industries produce substantial quantities of by- products, which could be easily used as animal feed supplements.
Unfortunately very little is used
Commonly available by-products are,
✓Sugar cane bagasse
✓Fruit and canary waste
✓Waste tea leaves
✓Poultry litter
Methods of overcoming the problems associated with the use of fibrous feed
There are a number of simple methods available to increase the palatability and
the digestibility fibrous feeds. These are:
1. Physical treatment
2. Chemical treatment
3. Supplementation
1. Physical treatment
Physical treatment methods alter the physical nature of the material, but not the chemical nature.
E.g. particle size. length, moisture content
1. Chopping
2. Grinding
3. Soaking the material in water
2. Chemical treatment
One or a combination of chemicals can be used in different ways. In these methods, structural changes of the fibrous material take place, due to chemical reactions.
The commonly used chemicals are
Caustic soda
Caustic potash
Urea
Wood ash
3. Supplementation
The nutrients that are deficient in fibrous feeds are provided through other feed sources. Concentrate, mineral mixtures, urea, and tree fodder are generally used.
Supplementation with cheap and readily available resources is the most convenient, economic and efficient method that can be practiced by farmers.
Practical guidelines for use of rice strows as ruminant feeds
Collection and storage of rice straw: Rice straw is a seasonally available feed resource. In certain areas of Sri Lanka, straw is produced twice a year.
Preserve the keeping quality
Straw must be collected as soon as possible after the rice is threshed,
properly dried before storing
store in a manner that will protect it from rain.
Wet straw allows moulds to develop and soon becomes unsuitable for livestock feeding
Mouldy straw is unacceptable to ruminants and if consumed, it may lead to certain metabolic disorders or toxicities due to presence of mycotoxins.
Well-dried straw when suitably stored can be kept for nearly 2 years without deterioration of its original nutritive value or acceptance by the animal.
Well-dried straw can be made into square bales or loosely stacked in a hay barn or similar structure.
Straw must be stored in a manner that will allow proper cross-ventilation, or heaped on a rock or on woody platform as in the "Kolaya" method.
Precautions must be taken to prevent termite damage, by stacking on an elevated base.
Methods of treatments of straws and stover
Straws should be chopped into 8-10 cm lengths, before feeding.
Stover which are thicker and coarser, need to be chopped into lengths of 4-6 cm.
Chopping alone will not improve the intake because of the coarse nature of the material.
It is important to improve the texture by soaking the chopped material in water for 6 - 8 hours before feeding.
The amount of water is 1 bottle (750 cc) for every kg of fibrous feed.
Sprinkle water on the feed
This method of treatment will improve the feed intake by 30 - 40%.
This will not only improve the palatability but also remove certain detrimental water soluble compounds (oxalic acid in rice straw).
One disadvantage is that along with the detrimental substances some of the water soluble nutrients, (sugars and proteins) may also be lost.
Chemical treatment
This can be done with caustic soda (NaOH), caustic potash (KOH), burnt lime (CaO) or urea [(NH2)]2CO.
The cheapest, least hazardous and most convenient method is treatment with urea-ammonia.
This method was popularized some years ago in Sri Lanka, but did not find acceptance by farmers because of practical difficulties in adopting this method in small farms.
Today, in many developing countries, this method is widely used to improve
fibrous feeds.
The chemical generally used is fertilizer grade urea.
Methods of treatments
1. Chopped straw or stover (straw may be used without chopping) is spread on a cemented floor or on a polythene sheet.
2. Sprinkle 4 % urea solution using a watering can or a tin with a perforated base.
3. Four percent urea solution is made by dissolving 40g of urea in 1 liter of water.
4. After treatment, the treated straw must be covered with a polythene sheet to prevent the escape of ammonia gas that is formed from urea.
Another convenient method of preventing the loss of ammonia, is to pack the treated straw into polytheine bags and tying the open ends.
The bags should be covered with a large polythene sheet and stored for 7 days to allow time for the urea to react with the straw.
The straw that is treated on day I, will therefore be ready for feeding only on day 7
The straw that is required for feeding on day 8 and thereafter should be treated daily starting from day 2
After 7 days of storage, open the polythene cover to expose the quantity of straw required for the day.
Prior to feeding, allow the treated straw to remain exposed for 0.5 - 1 hr to facilitate the liberation of excess free ammonia.
Urea treated straw must be introduced to animals gradually, offering 10% of the total feed and daily increasing the amount offered so as to allow time for the animal to adapt to the new feed over a period of 7 to 10 days.
Importance of points to remember
1. Collect and properly store an adequate quantity of straw for drought feeding.
2. Treat straw daily to meet one days' requirement.
3. Do not feed refusals on the next day.
4. Do not exceed the concentration of urea solution more than 4%.
5. Do not feed treated straw as soon as the polythene covering is opened. Animals may refuse to eat.
6. Continue feeding of treated straw until grass becomes available and withdraw the feeding of treated straw gradually as grass becomes available.
7. When feeding urea treated straw, it is important to provide a readily available energy feed like concentrates.
This should form at least 10% of the total basal ration (100g of concentrate per kg of dry straw).
But as concentrates are expensive, fresh grass rich in soluble sugars could be given with urea treated straw whenever possible in order to reduce the feed costs.
The alternative is to feed supplements such as molasses when urea treated straw is fed.
Supplementation
This method will help to provide nutrients that are deficient in rice straw and stover.
Supplementation will improve the quality of the ration in the following manner.
1. Optimizing the rumen by providing the limiting nutrients such as ammonia nitrogen, soluble sugars and minerals, to improve digestibility (catalytic effect)
2. Providing deficient nutrients to balance the low quality feed (supplementary effect)
Supplements do not change the structure of the fibrous feed, but facilitates its
utilization. It is an easier method for the farmer to practice than chemical treatment.
Feed can be harvested and offered to the animal on the same day.
The type of supplement to be fed will depend on the nutrients that are deficient in the basal feed.
Types of supplements
1. Urea
To provide rumen ammonia nitrogen.
2. Urea-molasses-mineral multi nutrient (UMMM ) mixture
To supplement rumen ammonia nitrogen, soluble sugars and minerals.
3. Concentrates
To supplement proteins, carbohydrates and minerals.
4. Tree fodder
To provide deficient proteins and soluble sugars.
Supplementation of urea
Urea could also be used as a supplement for fibrous feed.
This could be done through sprinkling urea solution on fibrous feeds or incorporating urea in the concentrate feed mixture.
Urea supplementation has proved to be equally effective as urea treatment when fed with fibrous feed.But the level of urea used must not exceed more than 1.0-1.5% of the total feed on dry matter basis. This could be achieved by sprinkling 1 to 1.5% urea solution (10 - 15g of urea dissolved in 1 liter of water) at the rate of 1 liter per 1 kg o f straw.
Urea sprinkled straw could be fed after 2-3 hours of sprinkling.
In the event that excess urea is consumed, the animal will exhibit symptoms of ammonia toxicity such as purple or blue coloration of the mucous membrane of the mouth, muzzle and eyes.
In such a situation, administer 1-1.5 liters of vinegar orally and summon a veterinary surgeon.
UMMM provide complete supplementation of nitrogen, energy and minerals.
This is made by mixing
Molasses - 35-45 %
Rice bran - 30-40 %
Urea -10-12 %
Minerals - 3-5 %
The exact composition of the UMM and the form (bricks or flakes) could be varied to suit the feeding practices under different production systems.
Concentration feeding
Most common method of supplementation.
Commercial concentrate feeds are readily available in the market place.
Farmers often prepare concentrate mixtures using commonly available ingredients, such as coconut poonac and rice bran.
Even when mixed on farm, concentrates are the most expensive feed available for milk production.
As a general rule, 1 kg of concentrate is given for maintenance and thereafter, an additional 1kg is provided for every 2 liters of milk produced.
Feeding of tree fodder
Feeding of tree fodder is an another economical and sustainable method of supplementation.
The farmer does not have to invest or spend money to obtain this valuable supplement.
This is either generally freely available or can be easily cultivated in homesteads along fences.
Tree fodder can be either legumes or non-legumes.
The common tree fodder species
1. Vetahiriya (gliricidia)
2. Erabadu (erythrina)
3. Ipil-ipil (leucaena)
4. Calliandra
5. Murunga (drum sticks)
6. Thiththa Sooriya (wild sunflower)
7. Mulberry
8. Maila
9. Gansooriya
10. Wehimara (raintree)
11. Kos (jak)
12. Kapok
13. Wada (shoe flower)
14. Kohomba (neem)
These have certain limitations when used as feed that are specific to each variety.
They are high in lignin and some contain chemical substances that may be toxic to animals, when consumed in excess.Therefore, the use of tree fodder as the sole feed should be limited
Generally, tree fodder can be satisfactorily included at a level of between 30 - 40 % in the diet.
In certain areas, 2-3 liters of milk per day is obtained by feeding a combination of grass and tree fodder, without resorting to concentrate feeding.
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